Search PubMed⌕ Search

Biomedical subjects

A Paci

Publications and source records attributed to A Paci.

At least 37 records · Page 2Linked to original sources
PubMed1996

Different methods for measuring endogenous digitalis-like factor(s).

It is well recognized that one of the difficulties in the search for endogenous ligand(s) with digitalis-like properties (endogenous digitalis-like factor(s), EDLF) in mammals has been the lack of a unique, specific method for the accurate measurement of EDLF. Using C18 solid-phase extracts of plasma from normal adults and various patient groups, and purified extracts from umbilical cord plasma by affinity resin chromatography and HPLC, different methods to measure EDLF were evaluated. These were: (a) a human placenta radioreceptor assay (RRA) developed on the premise that competition for cardiac glycoside receptors was an absolute requirement for EDLF; (b) the inhibition of 86Rb uptake in human erythrocytes to estimate the potassium transport by the sodium pump; (c) an enzyme immunoassay specific for ouabain recently introduced in the market (DuPont Ouabain EIA Reagent Pack). The human placenta RRA was found to have the same ease of application as immunoassay, but could have major advantages in detecting active molecules, being "biologically more meaningful". Ouabain immunoreactivity correlated with EDLF values obtained by RRA, but in some instances the two assays were completely unrelated. Moreover, the high specificity of the DuPont antibody for ouabain (< 3% cross reactivity with digoxin) could be disadvantageous to detect EDLF not strictly resembling ouabain. The 86Rb uptake inhibition method correlated with RRA for EDLF purified by HPLC. It tested the complete enzymatic cycle and could therefore better reflect the in-vivo inhibitory activity of EDLF. However, it appeared not suitable for the routine EDLF evaluation in clinical studies since it was susceptible to sample osmolarity and required daily isolation of human erythrocytes possibly from the same donor. Results of the present study demonstrate that every assay has its limitations, and would suggest the use of multiple assays for EDLF detection.

Cardenolides↗
PubMed1996

Mitochondria act as a reservoir for the basic amine HIPDM in the lung.

The lungs are a site for the uptake, accumulation, and storage of exogenous basic amines. The compound N-N-N'-trimethyl-N'-(2-hydroxy-3-methyl-5-iodobenzyl)-1,3 propanediamine (HIPDM) is a basic amine that can be labelled with radioactive iodine and detected by external counting. Intravenously injected 123I-HIPDM is extracted by the human lung, where it is retained in a slowly effluxable pool. In the present study, we measured HIPDM lung kinetics and subcellular distribution in rabbits given i.v. 125I-HIPDM. Rabbits were killed from 2 min to 5 h after injection, and the radioactivity retained in their lungs was measured. Subcellular lung fractions (nuclear, mitochondrial, lysosomal, microsomal and postmicrosomal supernatant) were assayed for HIPDM radioactivity, protein content, and distribution of specific marker enzymes. HIPDM lung clearance in rabbits was nearly identical to that of humans. Virtually all the HIPDM radioactivity in lungs (98+/-1%) was associated with subcellular membranous structures. The highest HIPDM specific radioactivity was found in the mitochondrial fraction, and the subcellular distribution profile closely resembled that of the mitochondrial marker enzyme succinate cytochrome c reductase. No redistribution of HIPDM among subcellular compartments was observed over a 5 h period after injection. The data indicate that mitochondria act as reservoir for HIPDM in the lungs and contribute to the pulmonary persistence of this compound. HIPDM can be used to investigate the pulmonary uptake of basic amines in health and in lung disease.

Animals↗
PubMed1996

Human placenta radioreceptor assay with digoxin and ouabain to detect endogenous digitalis-like factor(s) in human plasma and urine.

We describe the optimization and validation of a clinically feasible radioreceptor assay to detect endogenous digitalis-like factor(s) (EDLF) in human plasma and urine. The assay is based on the competitive replacement of 125I-labeled digoxin on human placenta membranes by ligands present in sample extracts. Digoxin and ouabain were used as calibrators. We also describe simple and effective methods for extraction and enrichment of EDLF from human plasma and urine. Assay sensitivity and precision were enhanced by using a sequential saturation technique with appropriate concentrations of tracer and receptors. Filtration was used to separate bound from free ligand. A two-step solid-state extraction with acetonitrile allowed the separation of two EDLFs with different polarity (EDLF-1 and EDLF-2) from the same plasma sample. A one-step solid-state extraction with methanol was suitable for urine. EDLF-1 and EDLF-2 in healthy adults were respectively 204 +/- 155 and 207 +/- 423 pmol/L ouabain equivalents, or 312 +/- 241 and 302 +/- 581 pmol/L digoxin equivalents. Plasma concentrations of EDLFs in newborns and pregnant women were higher than in healthy adults, and the concentrations in urine were higher than in plasma. Several cross-reactivity experiments showed that physiological concentrations of endogenous steroids and lipids did not inhibit binding, and supported the hypothesis that EDLFs are endogenous compounds other than the steroids and lipids also investigated.

Acetonitriles↗
PubMed1995

[Propafenone and flecainide in the therapy of ventricular arrhythmias].

Flecainide and propafenone are antiarrhythmic drugs of the class 1C (Vaughan and Williams) commonly used for ventricular arrhythmias. The purpose of the present study was to evaluate the efficacy of these drugs in 170 consecutive patients with ventricular arrhythmias who referred to our cardiological ambulatory. The study population was divided into two groups according to the absence (group A,82 patients) or presence of organic heart disease (group 1B: 51 patients with left ventricular ejection fraction (LVEF) >35%; group 2B: 37 patients with LVEF<35%). Ventricular arrhythmias were evaluated with a 48 hours Holter monitoring at baseline, and with a control 24 hours Holter monitoring at 15 days (for optimizing the dosage), at 5 months and at 10 months from the beginning of antiarrhythmic therapy. Patients of group A were randomly assigned to antiarrhythmic treatment (flecainide 150-300 mg/die or propafenone 450-900 mg/die). For patients of group B, such choice was leaded by the clinical and strumental data (32 patients were treated with flecainide, 56 patients with propafenone). In the 160 patients who ended the 10 months follow-up, we observed the following results: patients of group A showed a mean percentage reduction in incidence of premature ventricular complexes (PVC) after therapy in comparison to basal conditions of 93% and 89% with flecainide and propafenone, respectively, after a treatment of 5 months (p < 0.001); after 10 months mean percentage reduction of PVC was 91% with each drug (p = n.s.); complex ventricular events (CVE) were reduced of 90% and of 100% after 5 and 10 months, respectively, of treatment with flecainide and of 100% both after 5 and 10 months of treatment with propafenone (p = n.s.) -- patients of group 1B showed a mean percentage reduction of PVC of 87% and 84% after 5 and 10 months, respectiively, of treatment with propafenone (p = n.s.); after 5 months of therapy mean percentage CVE reduction was 66% with flecainide and 86% with propafenone (p < 0.001); after 10 months this mean reduction was 53% with flecainide and 73% with propafenone (p < 0.001). -- patients of group 2B showed a mean reduction of PVC of 59% and 58% after 5 and 10 months of therapy with flecainide, and of 65% and 67% after 5 and 10 months of therapy with propafenone (p = n.s.); CVE were reduced of 28% with flecainide and of 47% with propafenone after 5 months of treatment (p < 0.001) and of 36% with flecainide against 52% with propafenone after 10 months (p < 0.01). In the present study there was no significant difference between the two drugs in terms of tollerance and collateral effects (8% with flecainide vs 7%, with propafenone). Our results confirm the efficacy of the 1C class drugs in the treatment of "essential" ventricular arrhytmias. This efficacy appears reduced in non selected patients with organic heart disease. In these latter patients propafenone has shown more efficacy than flecainide in reducing CVE.

Adult↗
PubMed1994

[Growth factors and oncogenes in development and carcinogenesis. Role of the epidermal growth factor system].

The processes of cellular proliferation and progressive acquisition of a specialized phenotype show a remarkable degree of coordination that involves both intracellular programming and intercellular communication. One of the major incentives for studying factors that regulate the processes of cellular proliferation and differentiation is the recognition of their potential contribution to tumorigenesis. In normal cells, stimulatory and inhibitory events are believed to be under the control of growth factors and growth inhibitory factors, which are known to be protooncogene products. Growth regulatory mechanisms usually involve the binding of a growth factor to a specific receptor on the cell surface, which then through an intracellular biochemical cascade leads to cell division. The cell regulation pathways initiated by growth factors may be subverted at several distinct levels in cancer cells. Studies of oncogenes have shown that they may function as abnormal growth factors or abnormal receptors, induce expression of potential signal regulators or encode proteins which modulate gene transcription. The purpose of the present paper is to examine the role of growth factors, growth factor receptors and intracellular proteins involved in signal transduction (with particular regard to the epidermal growth factor receptor system) in the control of normal growth and differentiation, and their contribution to transformation and tumorigenesis. We also review the classical theories of neoplasia and various other models. Chemical carcinogenesis and Vogelstein-Lane model are presented.

Amino Acid Sequence↗
PubMed1993

Endogenous digitalis-like activity in the newborn.

Elevated levels of endogenous digoxin-like immunoreactivity have been reported in the body fluids of premature and full-term infants as well as in term pregnancy, in the amniotic fluid, and in human milk. Several lines of evidence suggest that these factors could also have biological properties in common with digitalis: i.e., they could represent truly endogenous digitalis-like factor(s). In recent years we succeeded in partially purifying this factor from umbilical cord blood, which represents an easily available source of this factor. The inhibitory activity of this factor on 86Rb uptake could be neutralized by antidigoxin antibodies (Fab fragments) and provided, for the first time, direct evidence of an association between digoxin-like immunoreactivity and biological digitalis-like activity. In addition, these antibodies could be used for immunoaffine chromatography as a purification step before separation by high-performance liquid chromatography. Preliminary experiments suggest that this endogenous compound has both a tissue and an isoenzyme selectivity and is not a well-known steroid (testosterone, progesterone, 17-OH progesterone, cortisol, dehydroepiandrosterone sulfate, and estradiol).

Animals↗
PubMed1992

Endogenous digitalis-like factors in human milk.

We measured the concentration of endogenous digitalis-like factors (EDLFs) in milk or colostrum of women during nursing on different days after delivery. EDLF concentrations were assayed by a solid-phase RIA involving antidigoxin antibodies and by a radioreceptor assay (RRA) involving human placenta Na+/K(+)-ATPase. The mean (SD) EDLF concentrations as measured by RIA were 35.6 (19.4) ng of digoxin equivalents per liter in milk samples (n = 37) and 61.3 (12.5) ng/L in colostrum samples (n = 5); the mean EDLF concentration as measured by RRA in milk samples (n = 11) was 573 (717) ng/L (range 0-2098). EDLF concentration in milk is greater than circulating concentrations in healthy adults but is comparable with serum concentration in the third trimester of pregnancy. In milk and serum samples (n = 8) collected at the same time, heating and (or) extracting with Sep-Pak C18 cartridges before the RIA produced significantly different EDLF values from those in untreated serum (P less than 0.001) and milk (P = 0.035). EDLF in milk appeared to be not bound or weakly bound to milk protein, as indicated by the fact that boiling did not increase the digoxin-like immunoreactivity.

Blood Proteins↗
PubMed1990

Endogenous digitalis-like factors: their possible pathophysiological implications with particular regard to the perinatal period.

Endogenous factors with biological and immunological activity similar to cardiac glycoside drugs (endogenous digitalis-like factors; EDLF) have been found in several tissues and body fluids of animals and humans. Detectable EDLF concentrations were found in blood and urine extracts of adults (normal healthy controls, hypertensive patients and salt-loaded healthy subjects), while higher levels were generally observed in plasma samples of pregnant women, newborns, and patients with renal insufficiency. The chemical characteristics of this endogenous factor are, at present, unknown, although it has been suggested that EDLF could be a substance with low molecular weight. Experimental studies and theoretical considerations suggest that EDLF, in addition to the ability to react with antibodies, might also bind to the specific cellular receptor of the cardiac glycosides and thus inhibit the membrane Na+/K(+)-ATPase (sodium pump). Therefore, it has been suggested that EDLF is an endogenous modulator of the membrane sodium-potassium pump, and that it could play a role in the regulation of fluids and electrolytes, in the myocardial muscular tone and also in the pathogenesis of hypertension.

Adult↗
PubMed1990

[Ventricular arrhythmias in the acute phase of myocardial infarct and in the postinfarct. A 1-year follow-up].

A total of 90 AMI patients (80 male, 10 female; mean age: 62 years, range: 36-70 yrs) who were admitted to the coronary care unit within six hours of the onset of symptoms were evaluated for the following: the incidence and variability of complex ventricular ectopic beats (classes Lown III-V) in the acute, subacute and chronic phases of myocardial infarction. The diagnostic utility of Holter monitoring and treadmill exercise testing was compared so as to reveal complex ventricular ectopic beats. The relation between complex ventricular ectopic beats and left ventricular dysfunction was determined using the echocardiographic technique (ejection fraction, fractional shortening). The hospital mortality rate was 6.6% (6/9 patients) while the post-hospital mortality rate was 3.5% (3/84 patients). The prevalence rate of complex ventricular ectopic beats detected by Holter monitoring was respectively: 85.5% (77/90 patients) in the acute phase, 8.5% (7/80) at the 72nd hour, 18.5% (15/80) in the pre-discharge phase. At 1, 3, 6 and 12 months the prevalence rate was respectively 35% (27/77 patients), 28.8% (22/77), 24.6 (19/77), 24.6% (19/77). A high variability in arrhythmic groups was found. Each group was composed of new arrhythmic patients and stable arrhythmic patients, in addition to a small number of patients who were arrhythmic in the preceding control but no arrhythmic in the following control. This specific analysis of various groups revealed that the pre-discharge phase is the period with the highest number of "stable arrhythmic" patients (4 Holter positive out of 5) compared to the 1st month (3 Holter positive out of 4) and the 3rd month (2 Holter positive out of 3).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Binding of 14C-furosemide to isolated human erythrocytes.

The incubation of 14C-furosemide at high specific activity with intact red blood cells at 37 degrees C, pH 7.4, has enabled the furosemide binding sites to be characterized with respect to time course, affinity and specificity. The binding reaction was rapid, reversible and close to thermodynamic equilibrium. Binding was dependent on cell and furosemide concentration and was saturable. At equilibrium, pharmacological doses of furosemide competitively inhibited 14C-furosemide binding with 50% inhibition at 3 x 10(-5) M. The Na+/K+ pump inhibitor ouabain had no effect on the 14C-furosemide binding. Bumetanide, which is more potent than furosemide as inhibitor of Na+/K+ co-transport system and equally effective in inhibiting anion transport, was less effective than furosemide in displacing 14C-furosemide from its binding sites, suggesting a different mechanism of action for the two drugs in the red blood cell. The preincubation of erythrocytes with 4,4'-diisothiocyano-stilbene-2,2'-disulphonic acid (DIDS), the potent and specific inhibitor of anion permeability, reduced specific furosemide binding by more than 80% at a furosemide concentration of 0.1 microM, while it had little effect on the non-specific furosemide binding. Taken together, these data suggest that furosemide interacts with specific binding sites in the human red blood cell, whose nature has not been clarified, but whose location is probably on (or near) the protein in band 3, i.e. the membrane macromolecule-mediating anion transport.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1989

Lung tissue binding of iodobenzyl-propanediamine: involvement of beta-adrenergic receptors.

The basic compound N-N-N'-trimethyl-N'-(2-hydroxy-3-methyl-5-iodobenzyl)-1,3- propanediamine (HIPDM) accumulates in human and rabbit lungs, where it forms a slowly effluxable pool. In isolated perfused rat lung, HIPDM is taken up by a saturable, energy-independent mechanism, which is competitively inhibited by imipramine, chlorpromazine and propranolol. To ascertain whether beta-adrenergic receptors are involved in the binding process of HIPDM to lung tissue, the ability of unlabelled HIPDM to displace the beta-adrenergic receptor ligand [125I]iodocyanopindolol (ICYP) from rabbit lung beta-receptors was examined. Lung microsomal membrane fractions (75 micrograms ml-1) were incubated at 37 degrees C for 3 h with 68 pM ICYP (with or without 1 microM of (+/-)-propranolol) in the presence of HIPDM (10(-10)-10(-3) M). Bound and free radioactivity were separated through glass-fibre filters and the retained radioactivity was counted in a gamma-spectrometer. HIPDM competed with ICYP for beta-adrenoceptors (13% displacement at 10(-5) M. 50% at 5 x 10(-5) M, and 90% at 2 x 10(-4) M). The inhibition curve of ICYP binding by HIPDM was similar to that observed for (-)-noradrenaline. Although the results of the in vitro studies cannot be extrapolated to in vivo conditions, they suggest that beta-adrenergic receptors may be involved in the observed lung uptake of the basic amine HIPDM.

Animals↗
PubMed1989

Nimodipine in acute ischemic stroke: a double-blind controlled study.

Nimodipine (BAY e 9736), a new dihydropyridine derivative, has been shown to reduce neurological deficits and mortality induced by acute cerebral ischemia in experimental studies. We investigated the effects of this calcium antagonist in patients with acute ischemic stroke through a randomized, double-blind, parallel-designed trial in which nimodipine was compared with placebo. Forty-one of 54 screened cases were found to fulfil the inclusion criteria (sudden occurrence of a focal neurological deficit secondary to an acute ischemic event in the carotid area diagnosed after a complete neurological work-up) and entered the study. Nineteen of them were treated with nimodipine (40 mg t.i.d. administered for 28 days) and the remaining 22 with placebo, given in identical tablets. In all patients the treatment started within 12 h after the onset of the symptoms. Course and intensity of the neurological deficit were evaluated by the Mathew Scale (slightly modified). Forty patients concluded the trial. Nimodipine was withdrawn in one case following the occurrence of a skin rash whose causative relation with the test drug could not be clarified. Altogether, however, nimodipine was well tolerated and no severe cardiovascular adverse reactions were observed. In terms of efficacy, the scores obtained by the Mathew Scale showed a higher rate of improvement on nimodipine than on placebo, thus indicating that patients receiving the latter drug did not fare as well as those receiving the test medication. Our data suggest that nimodipine may be beneficial in the treatment of acute stroke.

Acute Disease↗
PubMed1989

[Katacalcin levels in healthy children and children with spasmophilia].

The calcitonin (CT) gene encodes at least 3 peptides: CT, the 21-aminoacid carboxyl-terminal flanking peptide (katalcin or PDN-21) and CT-gene related peptide. Normal thyroid C-cells as well as malignant ones co-secrete CT and PDN-21 in response to hypercalcemia, so assay of PDN-21 may be an usefull method to assess C-cells secretion. Because of our knowledge no data are available on PDN-21 values in children, we measured this peptide in healthy children and in spasmophilia (Sp), a disease that has been related to CT deficiency. We studied 16 healthy children (9 males, 7 females; aging from 3.0 to 11.6 years) and in 21 patients with diagnosed Sp (8 males, 13 females, aging from 4.6 to 13.0 years). PDN-21 were assayed in whole serum by RIA using synthetic human PDN-21 for standards, 125I-PDN-21 for tracer and specific antiserum. CT was measured the serum of the same subjects by RIA using an ultrasensitive methods. In healthy children PDN-21 serum values were 12.3 +/- 2.0 pg/ml and no significant differences were found between males and females. Children with Sp showed slow higher PDN-21 concentrations (14.0 +/- 1.4 pg/ml) than normals, but the difference was not statistically significant. Also CT values were not significantly different between normal children (21.4 +/- 3.7 pg/ml) and patients with spasmophilia (22.5 +/- 1.8 pg/ml). A high significant positive relation was found between katalcacin and CT levels in normals as well as in spasmophilics. The physiological effects of PDN-21 are actually unknown.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1989

Specific binding of cardiac glycoside drugs and endogenous digitalis-like substances to particulate membrane fractions from human placenta.

We studied the characteristics of binding of cardiac glycosides to particulate membrane fractions from human placenta, to demonstrate that placental tissue is a suitable source of receptors for digitalis drugs. Moreover, we performed preliminary experiments with 125I-labeled digoxin and placental particulates to develop a radioreceptor assay for measurement of endogenous substances with activity similar to cardiac glycoside drugs (EDLS). Placental membrane fractions were incubated with [3H]ouabain (10 nmol/L) or 125I-labeled digoxin (50 pmol/L). With both ligands, binding followed a pseudo-first-order reaction kinetics and was saturable. Scatchard analysis revealed a single class of sites [for ouabain, KD = 20.2 +/- 5.8 nmol/L (mean +/- SEM), Bmax = 3.1 +/- 0.9 nmol per gram of protein; for digoxin, KD = 29.7 +/- 1.9 nmol/L, Bmax = 24.3 +/- 1.1 nmol per gram of protein]. As expected, digoxin was less potent than ouabain in displacing both tracers from digitalis drugs receptors; progesterone, cortisone, digitoxose, furosemide, bumetanide, and propranolol had no or little effect. Specific 125I-labeled digoxin binding was competitively inhibited by plasma and (or) urine extracts from newborns, adults, pregnant women, and patients with renal insufficiency. Inhibition of binding and volume of plasma and urine assayed were linearly related. These findings support the hypothesis that cardiac glycosides and EDLS can interact with the human placenta and suggest placental tissue to be a suitable source of receptors for cardiac glycosides.

Binding Sites↗